Republican Saxby Chambliss said Friday that he will retire from the U.S. Senate and not seek a third term in 2014, citing his "frustration" at partisan gridlock in Washington that has made it difficult to reduce the nation's mounting debt.

Chambliss, 69, was also facing a potential primary, but said in a statement that he believed he could survive challenges from fellow Republicans who would attack his record as a conservative.

"Instead, this is about frustration, both at a lack of leadership from the White House and at the dearth of meaningful action from Congress, especially on issues that are the foundation of our nation's economic health," Chambliss said. "The debt-ceiling debacle of 2011 and the recent fiscal-cliff vote showed Congress at its worst and, sadly, I don't see the legislative gridlock and partisan posturing improving anytime soon."

Chambliss was a member of the so-called "Gang of Six," a bipartisan group of senators that tried during the last Congress to forge an agreement on ways to reduce the debt, which is now at $16 trillion. The group's work was praised by President Obama, but its focus on a mix of spending cuts and tax increases -- which are reviled by within the Republican Party -- contributed to its collapse.

Chambliss's surprise announcement will likely send Republicans -- and Democrats -- scrambling for the open Senate seat. Republican congressmen Paul Broun and Tom Price were already thinking about running in a GOP primary and Jack Kingston, an 11-term House member, said Friday he'll consider the Senate race.

Democrats say they will make reclaiming the Georgia Senate seat a "priority" in the 2014 election cycle. They have a 55-45 voting advantage in the Senate and will defend 20 seats next year.

"Georgia will now offer Democrats one of our best pickup opportunities of the cycle," said Guy Cecil, executive director of the Senate Democrats' campaign committee. "There are already several reports of the potential for a divisive primary that will push Republicans to the extreme right. Regardless, there's no question that the demographics of the state have changed and Democrats are gaining strength."

Chambliss was first elected to the Senate in 2002 after serving in the U.S. House for four terms. He defeated Democratic incumbent Max Cleland, a Vietnam veteran and triple amputee, in a bitter race.

Chambliss took heat from Democrats -- and fellow Republicans such as John McCain -- for running a controversial ad against Cleland that included images of the Democrat, Saddam Hussein and Osama bin Laden. McCain, a prisoner of war in Vietnam, called the ad "worse than disgraceful."

In 2008, Chambliss had a closer-than-expected fight against Democrat Jim Martin. Chambliss defeated Martin in a runoff because he did not have the votes to do so outright on election night.

More recently, Chambliss voted this month for the bill to avoid the "fiscal cliff." That deal has angered some conservatives because it raised taxes on couples making over $450,000.